Inkjet printing typically involves ejecting inks from a component of an inkjet printer (e.g., from one or more nozzles of a printhead) onto a substrate.
Inkjet printhead nozzles can be designed to operate within specific viscosity ranges of inks and initial evaporation can generally cause an increase in viscosity that affects the ability of the nozzle to fire a drop of ink. Clogging can be caused by evaporation of an organic solvent or water from the interface of the liquid at the surface and/or within the nozzle. The inception of clogging may cause distortion of the printed image or alphanumeric character. Eventually the clogged nozzle can fail to fire and no image will be generated. Consequently, a printer service routine, such as a printhead purge operation, may be required on a regular basis to avoid printing defects. However, it may be desirable to service the printhead as infrequently as possible, as servicing the printhead can be wasteful of ink and requires that the printer be unavailable for normal printing operations.
A typical requirement for an inkjet ink is the ability to remain in the fluid condition in a printhead nozzle opening on exposure to air, which is the so-called “decap” condition. This ability can allow a nozzle to function normally after a period of non-use. Examples of such periods of non-use may be during times of printer storage, maintenance, and/or during normal operation of infrequently utilized printhead nozzles. Decap is sometimes referred to in the art as “latency” and these two terms have been used interchangeably. The longer the decap time rating of the ink, the longer the down times that can be handled or accommodated by the printer. For example, a long decap time reduces the need for servicing the printhead.
A longer decap time can be achieved, for example, by the use of certain less volatile solvents (a solvent with a lower vapor pressure) in the ink formulation. However, such solvents do not dry quickly enough for high throughput printing operations and thus smearing of the print may result. Therefore, there is a need for inkjet inks that permit longer decap time without sacrificing other beneficial properties, such as fast drying time.